Catalysis by ATP synthase: mechanistic, kinetic and theromodynamic characteristics

Abstract

Mechanistic,kinetic and thermodynamic aspects of ATP synthase have been determined and analyzed.Reversibility and inversibility of catalysis in ATP synthasis represent two contrasting modes of catalysis with important implication for the modicuar mechanisim of ATP synthasis.To shed light on these aspects,we have developed kinetic schemes for ATP synthesis of hydrolysis analysis of these scheme reveals several novel features and provides new directions for further research. First the ratio of bound 32p1to total bound 32p can be expressed in terms of the rate constent of the elementry catalytic steps,which are characteristic properties of the system,therefore result the classical cold chase/acid quench 32p1 exprement interpreted in terms of an equilibrium distribution of bound subsrate and product at the catalytic site can be explained by an inversible mode of catalysis.Second characterization of the mechanistic and kinitic properties reveals and absence of cooperativity in ATP synthase and the product release presedes substrate binding.Third,APH and are kinetically inequivalent in driving ATP synthesis and is not the true driving force for ATP synthesis.Thermodynamic analysis of ATP synthesis reveals a dynamically electrogenic but overall electroneutral mode of ion transport across the membrane.The p/o ratio based on the torsional mechanism was obtained was shown to explain the expremental observation of the past 50years and to be in agreement with the thermodynamic calculation.Taken together,these finding necessitate a paradigam shift for understanding the molecular mechanism of ATP synthesis.